A healthy immune system is a finely balanced system: too little activity and we fall prey to disease, too much, and it attacks our own tissue, triggering autoimmune diseases like multiple sclerosis. Now three studies published online this week in Nature suggest the amount of salt we eat may influence this balance by indirectly encouraging the overproduction of immune cells. In the three studies the researchers focused on a group of immune cells known as T cells because they play an important role in clearing disease-causing pathogens and also in autoimmune disease. They were particularly interested in how T cells develop.